This project is concerned with analyzing the cell-to-cell contacts and the internal organization of the synaptic membranes in the retina, using electron microscopy of thin-section specimens, instantaneous freezing at 4 degree K and the freeze-fracturing technique. Experiments are designed which will help to understand the functional significance of the intramembrane differentiations in the photoreceptor cell synapses, and their role in the events of synaptic transmission. Finally, attempts will be made to separate from the retina a highly enriched population of viable photoreceptor cells and to develop a split-retina preparation in order to investigate the process of transmitter release and synaptic vesicle membrane recycling in the photoreceptor endings.